21172649 has 2 divisors, whose sum is σ = 21172650. Its totient is φ = 21172648.

The previous prime is 21172643. The next prime is 21172651. The reversal of 21172649 is 94627112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20976400 + 196249 = 4580^2 + 443^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21172649 is a prime.

Together with 21172651, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21172643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10586324 + 10586325.

It is an arithmetic number, because the mean of its divisors is an integer number (10586325).

Almost surely, 2^21172649 is an apocalyptic number.

It is an amenable number.

21172649 is a deficient number, since it is larger than the sum of its proper divisors (1).

21172649 is an equidigital number, since it uses as much as digits as its factorization.

21172649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 32.

The square root of 21172649 is about 4601.3746858955. The cubic root of 21172649 is about 276.6464272867.

The spelling of 21172649 in words is "twenty-one million, one hundred seventy-two thousand, six hundred forty-nine".